Closed Caption Support - What You Need to Know to Comply with the 21st Century Communications and Video Accessibility Act (CVAA)

On April 30, 2012 new rules went in to effect governing accessibility standards for Internet video. These rules require the use of closed captioning for online distribution of video that was aired on TV (broadcast, cable, or otherwise).
48M people in the US (up to 15% of your site’s visitors) are deaf or have some degree of hearing loss. Providing accessibility extends your audience reach in the deaf community, as well as helps you meet legal requirements. But closed captioning technology can appear complicated and obscure. How can a publisher understand captioning technology, comply with the new legislation, and make caption support an easy part of video workflow?
Captions at Zencoder - Help Test Beta Closed Caption Feature
Zencoder provides support for Apple HTTP Live Streaming (HLS) captions, for iPad, iPhone, and for other devices that support HLS captions. We also offer support for the safe harbor format, DFXP/SMPTE-TT. If you're interested in learning more about closed caption support, contact us.
The Guidelines
The FCC rules go into effect in stages, and the National Association of the Deaf has a helpful guide for understanding this schedule. By the following dates, content providers must provide full support for captioning.

September 30, 2012: Prerecorded TV programming that has not been edited for Internet distribution

March 30, 2013: Live and near live programming that was recorded within 24 hours of broadcast on television;

September 30, 2013: Prerecorded programming that is edited for Internet distribution

By September 30, 2013, 100% of new video programming shown on television with captions must have captions when shown online.
There is a different schedule for archived programming that is re-aired on TV, and subsequently distributed online. Full caption support must be provided by the following dates:

The programming must be captioned within 45 days after the date it is shown on television with captions on or after March 30, 2014;

The programming must be captioned within 30 days after the date it is shown on television with captions on or after March 30, 2015;

Such programming must be captioned within 15 days after the date it is shown on television with captions on or after March 30, 2016.

And it's not just content that is under the perview of the new regulation. Device manufacturers have responsibilities as well. By January 1, 2014, all devices that play back Internet video must support closed captioning.
Are captions the same as subtitles?
There is a lot of confusion and ambiguity around subtitles and closed captioning. They are not the same, though the technology is converging. Technically, captions are intended to make video accessible to the hard of hearing, and often include more than just dialog: a caption track may include cues about who is speaking or mention other sounds (background music, a knock at the door). Subtitles are used for translation: making dialog understandable to someone who doesn't understand the spoken language. Theoretically, subtitles wouldn't need to mention that there was a knock at the door, because the viewer would hear that, regardless of whether or not they speak the language.
Beyond this, there are other differences between subtitles and captions. Subtitles are often included externally to a video stream, whereas captions have historically been encoded directly into the video; if you've ever seen white lines in the overscan area of a video, that is how closed captions are transmitted for broadcast content. Another way to slice it: captions are a TV setting, decoded from the broadcast video stream itself, whereas subtitles are a DVD option, where a user can choose an subtitle language (or no subtitles). So the two have historically used different technology, though for internet delivery, the technology is converging.